Just like pure water is obtained from ordinary water by a process called distillation which involves the use of sterilized apparatus, so a person attains purity of life by undergoing the process of sanctification which can only be brought about by God Himself through the Holy Spirit working through the Bible. The life too has to be lived out practically and not just fancied.
Whereas all kinds of religions have various ways through which their members are sanctified, the Bible sets out a standard by which we can know whether or not we are leading a holy life. The apostle Paul, the great apostle to the gentiles, writing to the Romans, makes it crystal clear that we all stand condemned before God, whether we are religious or irreligious and the only way through which this condemnation can be lifted is by faith in the Lord Jesus Christ. This is necessary because by nature we are all unclean and God is of purer eyes that He cannot look favorably upon evil. The Old Testament uses figures and types to refer to this state of man and declares that nothing unclean is ever acceptable in the sight of our holy God. In the book of Leviticus 11, God commands the children of Israel not to eat unclean animals lest they should be defiled. These animals, I believe, are used figuratively to mean the unregenerated nature of mankind which must be repented of if we have to be holy and blameless before God; this becomes possible only by His grace. Isaiah 64:6 shades light on the issue when it states: “But we are all as an unclean thing and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind have taken us away.”
Only after we have dealt with the impurities in our lives can we begin to experience holiness and the immediate evidence of this is the ineffable flow of peace in us. “Therefore being justified by faith we have peace with God through our Lord Jesus Christ (Romans 5:1). It is an indescribable kind of peace because we experience it even in difficulties and are able to behave differently from those who are yet to be justified. The peace and constancy we now express spring from our real hope of eternal life and the fact that the Lord Jesus is with us always.